Digital/analog conversion device and display device having the same

a conversion device and digital analog technology, applied in the direction of code conversion, instruments, pulse techniques, etc., can solve the problems of increasing consumption current, complicated circuit configuration, and affecting the effect of conversion speed

Active Publication Date: 2010-03-30
TRIVALE TECH LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The solution enables low power consumption and simple circuit configurations for generating analog voltages that change at regular intervals, improving the speed and accuracy of gray-level voltage generation for display devices.

Problems solved by technology

Such a ladder-type digital / analog conversion device, however, has a problem that the consumption current increases due to a constantly flowing DC current.
Therefore, in order to set the output voltage Vout in such a manner that the output voltage changes at regular intervals, it would be necessary to control the number of clocks to be input to the charge pump circuit according to the level of the output voltage Vout, possibly resulting in a complicated circuit configuration.
It is expected that this problem becomes noticeable when the digital / analog conversion device is employed for generating a gray-level voltage for a display device.

Method used

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  • Digital/analog conversion device and display device having the same
  • Digital/analog conversion device and display device having the same
  • Digital/analog conversion device and display device having the same

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0040]Referring to FIG. 1, a digital / analog conversion device 10 of a first embodiment includes a pulse number control circuit 20, a charge pump circuit 30, and precharge switches 51-53 serving as a precharge circuit. Digital / analog conversion device 10 generates, according to input digital data, an analog voltage VNo on an output node No to which an output capacitor 5 is connected.

[0041]In this embodiment of the present invention, it is supposed that the input digital data has 4 bits, namely the input digital data is constituted of weighted data bits D0-D3 among which data bit D0 is the least significant bit (LSB) and data bit D3 is the most significant bit (MSB), and a description of this embodiment will be given accordingly.

[0042]As clearly seen from the following description, the number of bits of input digital data is not limited to the above-described one and the digital / analog conversion device of the present invention may be configured to be adapted to digital data of an arb...

second embodiment

[0082]Output voltage VNo of the digital / analog conversion devices of the first embodiment and the modification thereof includes, as shown in Equation (4), capacitances Cp and Co and threshold voltage VTN. In usual, capacitances Cp and Co have low temperature dependency and are usually canceled in Cp / (Cp+Co) of Equation (4). On the other hand, threshold voltage VTN has relatively high temperature dependency so that output voltage VNo could vary according to an increase in operating temperature of the digital / analog conversion device. In a second embodiment, a configuration for solving the above-discussed problem is described.

[0083]Referring to FIG. 7, a digital / analog conversion device 12 of the second embodiment differs from digital / analog conversion device 10 shown in FIG. 1 in that the former includes a charge pump circuit 130 instead of charge pump circuit 30. Charge pump circuit 130 differs from charge pump circuit 30 in that the former includes a bias circuit 140 instead of bia...

third embodiment

[0095]Regarding the digital / analog conversion devices according to the second embodiment and the modification thereof, voltage VB which affects output voltage VNo includes the element (VTN−|VTP|) as seen from Equation (7).

[0096]Threshold voltages VTN and |VTP| each of the transistor could vary depending on process variation in manufacturing. If the influence of the variation causes the value determined by (VTN−|VTP|) to vary, the level of output voltage VNo could vary due to the variation of the transistor characteristics (threshold voltages). With a configuration of a third embodiment, the above-described problem is solved and thereby output voltage VNo is more accurately set, as described below.

[0097]Referring to FIG. 9, a digital / analog conversion device 14 of the third embodiment differs from digital / analog conversion device 12 shown in FIG. 7 in that the former includes a charge pump circuit 132 instead of charge pump circuit 130. Charge pump circuit 132 differs from charge pum...

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Abstract

A pulse number control circuit inputs, to a charge pump circuit, pulses of a number according to digital data constituted of weighted data bits. The charge pump circuit includes a pump capacitor connected between a first node to which the pulses are input and a second node, a switch element connected between the second node and an output node, and a bias circuit. According to a change of a voltage on the output node, the bias circuit changes a voltage on the second node with the same polarity.

Description

RELATED APPLICATIONS[0001]This application is a divisional application of Ser. No. 10 / 802,771, filed Mar. 18, 2004, now U.S. Pat. No. 7,236,152 which claims priority of Japanese Patent application Serial No. 2003-151079, filed May 28, 2003, the contents of which are hereby incorporated.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a digital / analog conversion device converting digital data into an analog voltage as well as a display device indicating a gray level with the analog voltage generated by the digital / analog conversion device.[0004]2. Description of the Background Art[0005]A digital / analog conversion device which converts digital data into analog signals is commonly used. Such a digital / analog conversion device is used, for example, for generating an analog voltage so as to display a gray level (this voltage is hereinafter referred to as “gray-level voltage”) on a display device having, for each pixel, such a voltage-driven...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): G09G3/36G09G3/30G02F1/133G09G3/20G09G3/32G09G5/10H01L51/50H03K17/06H03M1/12H03M1/66H03M1/76H03M1/82H03M1/86H05B33/14
CPCG09G3/3688H03M1/82G09G3/3233G09G3/3291G09G2310/0248G09G2310/027G09G2320/041G09G2300/0842H03M1/76
InventorTOBITA, YOUICHIODOI, YUZO
OwnerTRIVALE TECH LLC